Re: [PATCH v13 02/18] drm: bridge: panel: Support nodrm case for drmm_panel_bridge_add

From: Jagan Teki <jagan@amarulasolutions.com>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>,
	Inki Dae <inki.dae@samsung.com>,
	 Marek Szyprowski <m.szyprowski@samsung.com>,
	Seung-Woo Kim <sw0312.kim@samsung.com>,
	 Kyungmin Park <kyungmin.park@samsung.com>,
	Frieder Schrempf <frieder.schrempf@kontron.de>,
	 Tim Harvey <tharvey@gateworks.com>,
	Adam Ford <aford173@gmail.com>,
	 Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Marek Vasut <marex@denx.de>,
	 Matteo Lisi <matteo.lisi@engicam.com>,
	dri-devel@lists.freedesktop.org,
	 linux-samsung-soc@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	 NXP Linux Team <linux-imx@nxp.com>,
	linux-amarula <linux-amarula@amarulasolutions.com>,
	 Linus Walleij <linus.walleij@linaro.org>,
	 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Subject: Re: [PATCH v13 02/18] drm: bridge: panel: Support nodrm case for drmm_panel_bridge_add
Date: Mon, 27 Feb 2023 17:58:03 +0530	[thread overview]
Message-ID: <CAMty3ZDt64C0dv2=wVcaCLdZVFU2u6D4EKswuoqEjvByKyMseg@mail.gmail.com> (raw)
In-Reply-To: <20230227121149.c3ibajgog3i2s2ek@houat>

On Mon, Feb 27, 2023 at 5:41 PM Maxime Ripard <maxime@cerno.tech> wrote:
>
> On Mon, Feb 27, 2023 at 05:09:09PM +0530, Jagan Teki wrote:
> > drmm_panel_bridge_add DRM-managed action helper is useful for the bridge
> > which automatically removes the bridge when drm pointer is cleaned.
> >
> > Supporting the same on non-component bridges like host DSI bridge requires
> > a drm pointer which is indeed available only when a panel-bridge is found.
> >
> > For these use cases, the caller would call the drmm_panel_bridge_add by
> > passing NULL to drm pointer.
> >
> > So, assign the bridge->dev to drm pointer for those cases.
> >
> > Cc: Maxime Ripard <mripard@kernel.org>
> > Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > ---
> > Changes for v13:
> > - new patch
> >
> > Note: use case on
> > "[PATCH v13 04/18] drm: exynos: dsi: Switch to DSI panel or bridge find helper"
> >
> >  drivers/gpu/drm/bridge/panel.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
> > index d4b112911a99..45a0c6671000 100644
> > --- a/drivers/gpu/drm/bridge/panel.c
> > +++ b/drivers/gpu/drm/bridge/panel.c
> > @@ -402,6 +402,13 @@ struct drm_bridge *drmm_panel_bridge_add(struct drm_device *drm,
> >       if (IS_ERR(bridge))
> >               return bridge;
> >
> > +     /*
> > +      * For non-component bridges, like host DSI bridge the DRM pointer
> > +      * can be available only when a panel-bridge is found.
> > +      */
> > +     if (!drm)
> > +             drm = bridge->dev;
> > +
>
> Why can't the caller use bridge->dev?

The first step of drmm_panel_bridge_add is to find the panel-bridge,
so we can only get bridge->dev after this step. The caller doesn't
know anything about the panel bridge it just sends a panel pointer to
find the panel-bridge and then assigns bridge->dev to drm for DRM
action.

Please check this patch about the caller,
https://patchwork.kernel.org/project/dri-devel/patch/20230227113925.875425-5-jagan@amarulasolutions.com/

>
> Also, where did the devm_drm_of_dsi_get_bridge go? I thought you were
> going to convert it to a drm-managed version?

Look like your suggestion to can't use devm_drm_of_dsi_get_bridge and
call the DRM-action from the driver, that is the reason I have removed
this and done the same as your previous inputs.
https://lore.kernel.org/all/20230203110437.otzl2azscbujigv6@houat/

Jagan.

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